REPRODUCTION
1. Reproduction is the process by which an individual multiplies by producing many
individuals of same kind. Reproduction may be Asexual or Sexual. In asexual
reproduction, gametes are not formed. It may be Fission , Sporulation, Budding etc.
Fission is the division of the parent body into two or many pieces and each piece
develop into an organism. Fission may be Binary fission (Amoeba, Paramecium Planaria
etc ) or Multiple fission ( Plasmodium ). Sporulation is the division of the nucleus into
many pieces and formation of many individuals. Budding is the formation of an
individual from the parent body ( Hydra ). Sexual reproduction involves formation of
gametes, fusion of gametes and development of zygote.
2. Seminiferous tubules are the functional units of the testis from which sperms are
formed. Primordial germ cells of seminiferous tubules produce sperms, Leydig cells
secrete androgens ( Testosterone ), and Sertoli cells or nurse cells nourish sperms. Sertoli
cells also secrete a hormone Inhibin to inhibit the secretion of FSH. Rete testis is the
network of tubules connection the seminiferous tubules in the central region of testis.
3. Secretion of the Prostrate gland makes the sperms active. The secretion of prostrate
gland contains calcium ions, phosphate ions and an enzyme Prpfibrinolysin. Cowpers
gland secrete a clear lubricating fluid. Normal pH of seminal fluid is 7.35 to 7.5.
4. Eggs develop in the Graffian follicles of ovary. Graffian follicles also secrete homones.
Naturally occurring oestrogens are Estrone, 17b estradiol and Estriol. Estradiolis the
potent female hormone. Corpus luteum is the ruptured graffian follicle. It secretes
Progesterone. Corpus albicans or Yellow body is the degenerating corpus luteum.
5. Fallopian tube is the site of fertilization. Unusual development of egg in the fallopian
tube is called Ectopic pregnancy. Endometrium is the inner vascularised lining of uterus
in which implantation takes place.
6. Zona pellucida is the non cellular covering of the egg. It is covered with follicle cells
which form the Corona radiata.
7. Menarche is the starting of menstrual cycle and Menopause is the stopping of menstrual
cycle
8. Parthenogenesis is the development of egg without fertilization. It may be Arrhenotoky
( only males are formed – Honey bee ), Thelytoky ( only females are formed – Gall fly )
and Amphitoky ( both male and females are formed – Aphids ).
9. Secretion of Seminal vesicle contains Prostaglandins which causes contraction of smooth
muscles of uterus. Fructose present in the seminal fluid is the source of energy for the
sperm.
10. Based on the amount of yolk egg may be Alecital ( without yolk – Mammalian egg ),
Microlecithal ( little yolk – Amphibian egg ) Megalecithal etc ( large amount of yolk –
Bird’s egg ). Cledoic eggs are shelled eggs ( Birds, Reptiles ).
11. Fertilizin is a glycoprotein present on the egg. Antifertilizin ( formed of acidic
aminoacids ) is present on the sperm head. Capacitation is the preparation of sperms for
fertilization. It starts from Acrosomal reaction. Hyaluronidase and Neuraminidase are
the hydrolytic enzymes present in the acrosome of sperm.
12. Artificial insemination refers to the artificial transfer of sperms into the female’s body.
Surrogate mother carries fertilized egg of another female in her uterus. Oral
contraceptives are
birth controlling pills. These are synthetic estrogens and
progesterons. Copper T is an Intra-uterine device ( IUD ) that release copper ions in the
uterus to prevent implantation.
13. Holoblastic cleavage is the complete division of Zygote ( Human egg ) and Meroblastic
cleavage is the partial division ( Insects, Reptiles ). Spiral cleavage is seen in nematodes,
rotifers, annelida and mollusca.
14. Morula is the 32 celled stage formed after cleavage. Blastula with a cavity is called as
Coeloblastula ( Frog ) and solid blastula is called Stereoblastula ( Neries ).
15. Fate map was developed by Vogt in 1925. It shows the fate of various germ layers.
16. Foetal membranes or Extra embryonic membranes are Amnion ( protection ) Chorion
( protection, nourishment and excretion ), Allantois ( respiration, excretion ) and Yolk
sac
( storage of yolk ). Human placenta is Haemochorial , Deciduous and Meta
discoidal.